Thermal Spa Cover

ABSTRACT

A thermal spa cover assembly [ 1000 ] includes an improved thermal spa cover [ 1100 ] having a first part [ 1111]  and a second part which is held together with a hinge [ 1150 ], for sealing and retaining heat from a tub [ 130] . Cover [ 1100]  is made of thermal insulation material to reduce conductive heat loss. It also employs a central gasket [ 1151 ] fits inside of the hinge [ 1150]  and is attached to the first part [ 1111]  to minimize gaps and heat loss. End gaskets [ 1157]  are employed at the ends of the hinge [ 1150]  to provide a better seal at the tub, spa cover interface. This seal is slightly wider than the openings, but is compressible to seal in the openings. A shield [ 1170]  is attached to the upper side of the cover [ 1100]  extending downward over the spa cover [ 1100]  and the tub sides  135.  It fits tightly around the full perimeter of the tub [ 1130] . Tie-downs sewn on top of the cover [ 1100]  secure the cover [ 1100]  to the spa tub [ 130] ; further preventing warmed air from escaping.

This application incorporates by reference and claims priority to U.S. provisional patent application Ser. No. 61/073,510 filed Jun. 18, 2008.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to an improved spa cover that provides improved heat insulation.

2. Discussion of Related Prior Art

Spa covers are widely used to cover spas, or hot tubs, to protect the water within the spa tub from dirt and contamination and to provide a heat barrier thus reducing the cost of operating the spa. Spa covers are various sizes and shapes, and are designed to rest upon the top edge of a spa tub. Spa covers are often made up of two connected, folding halves with a hinge provided on the top surface connecting the two halves. The hinge allows the spa cover to be folded onto itself for removal and storage.

Spa covers generally include a core material and an outer cover material formed around the core material.

During typical operation, the temperature of the water within the spa tub is kept at a high temperature in order to allow persons to bathe within the tub. However, since spas are often located outdoors and are designed to be used in all seasons, there is a large temperature difference between the water and the outside air. This temperature difference encourages a substantial heat transfer from the hot spa water to the colder outside air. The spa cover is made of two parts of an insulating material hinged together. Heat escapes through gaps between the spa cover and the rim of the spa and through gaps at the hinge where the two cover halves meet.

There have been some attempts to modify the cover to conserve heat. U.S. Pat. No. 5,022,101 “Thermal Cover for a Spa” issued Jun. 11, 1991 to Gosselin et al. employs a one-piece cover which snaps to the top of a spa. This addressed the loss of heated air. It did also address loss of energy through radiation. But it did not employ sufficient insulation to stop the permeation of heat through the cover.

Another patent aimed at reducing the loss of hot air was U.S. Pat. No. 5,373,590 “Spa Cover” issued Dec. 20, 1994 to Svae et al. This patent dealt with an inflatable spa cover and was not primarily directed toward heat conservation. It did not employ insulation to reduce conductive heat loss. It also did not address loss of heat due to radiation.

U.S. Pat. No. 6,938,281 B1 “Foldable Spa Cover and Lift Unit” issued Sep. 6, 2005 to Tudor employed a skirt which hung down from the spa cover around the top of the spa. This invention did conserve energy, however, it was designed with air gaps which allowed heated air to escape. It also did not address the problem of heat transfer through radiation.

Currently, there is a need for a spa cover which more efficiently holds in heat making the spa more economical.

SUMMARY OF THE INVENTION

The present invention may be embodied as an improved thermal spa cover assembly 1000 for covering a tub 130 having sidewalls 135 filled with heated water 3 having a lip 133 and sealing tub 130 at its upper lip 133 comprising:

-   b) a first part 1111 having a top surface 1117, the first part 1111     being constructed of a heat insulating material; -   c) a second part 1113 having a top surface 1117, the second part     being constructed of a heat insulating material; -   d) a hinge 1150 pivotally connecting the first part 1111 to the     second part 1113; -   e) a continuous shield 1170 connected at the top surface 1117 of the     first part 1111 and the second part 1113 extending downward from the     top surfaces 1117 adjacent to the tub sides 135 to make a gap free     seal between these surfaces reducing the escape of heat.

The present invention may also be embodied as a method of reducing heat loss from a tub 130 filled with heated water comprising the steps of:

-   a) providing an insulated first part having a top surface, the first     part being constructed of a heat insulating material; -   b) providing an insulated second part having a top surface, the     second part being constructed of a heat insulating material; -   c) pivotally connecting the first part to the second part; -   d) applying a continuous shield 1170 connected at the top surfaces     of the first and second parts, the shield 1170 sized and positioned     to hang down along side the tub 130, and -   e) placing the first and second parts and the shield 1170 over said     tub 130 to thermally insulate the hot water from the environment and     to collect and retain escaping hot gases.

BRIEF DESCRIPTION OF THE DRAWINGS

The advantages, various additional features, and nature of the invention will appear more fully upon consideration of the illustrative embodiment of the invention which is schematically set forth in the drawings, in which:

FIG. 1 shows a prior art spa cover and a spa tub.

FIG. 2 shows a cross sectional side elevational view of a prior art spa tub and cover.

FIG. 3 is a perspective view of one embodiment of the improved thermal cover according to the present invention.

FIG. 4 shows a cross sectional, side elevational view of the spa assembly according to the present invention as it would appear placed on a hot tub.

FIG. 5 is a plan view of the spa cover of FIGS. 3 and 4 as viewed from below.

FIG. 6 is a side view of the first part and the second part of a prior art spa cover of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

While the invention is open to various modifications and alternative forms, specific embodiments thereof are shown by way of examples in the drawings and are described herein in detail. There is no intent to limit the invention to the particular forms disclosed.

Theory

FIG. 1 is a view of a prior art spa tub 130 and cover 110 illustrating how heat escapes into the environment.

The cover 110 typically includes insulated foam formed into a first piece 111 and a second piece 113. There is usually a hinge 150 provided on the top surface 117 of the spa cover 110. Cover 110 rests on the tub lip 133. The hinge 150 connects the two pieces 111 and 113 which allows the spa cover 110 to be folded for removal and storage.

A small, typically 3″ in length, skirt 170 may attach to the side or underside of the spa cover 110. These are intended to protect the tub lip.

The main heat source is the heated water 3 in the spa tub as shown in FIG. 1. As with all gradients, heat transfer occurs from high temperature to low temperature objects. Most heat transfer occurs by movement of heat energy by a) conduction and b) convection. Loss of heat by these processes causes the need for continued heating of water 3, thereby causing additional expense. Since energy has become more expensive, and the fact that these are typically kept hot constantly, loss of heat can significantly add to the cost of owning a hot tub.

Conduction Heat Transfer

Conductive cooling is heat transfer by objects which physically touch each other.

FIG. 2 shows a cross sectional side elevational view of a prior art spa tub 130 and cover 110.

Heated water 3 is at a temperature. It physically touches air 5 above water 3 which is initially at a temperature lower than water 3. By conduction, heat transfers from the hot water 3 to the air 5 heating air 5.

Air 5 is in contact with spa cover 110 which is at an initial temperature lower than the air 5. Heat tries to flow from the hotter air 5 into spa cover 110. Since spa cover 110 is made of a thermal insulating material, it does not conduct heat well, so there is some amount of heat transfer from air 5 to cover 110; however it is a small amount and moves slowly. It may take a long time for heat to transfer into cover 110.

Spa cover 110 is in physical contact with air surrounding it, environment 7, (not marked on FIG. 2) which is at an ambient temperature. Since the temperature of the spa cover 110 is greater than the temperature of the environment 7, heat tries to transfer from the spa cover 110 into the environment 7. Again, the thermal material of the spa cover 110 minimizes this heat flow. Therefore, conductive heat transfer does occur, but over a longer period of time than compared with heat-conductive materials.

Convection Heat Transfer

Heat transfer by convection is when a fluid absorbs heat at one location, then moves to another location to release the heat by natural processes. This usually occurs when a cool fluid, which is more dense than a hotter fluid, falls to the bottom of a container. This is because it is denser than the surrounding fluid.

If it is heated at a given location, it becomes less dense, and floats above cooler fluid.

As it releases heat (usually at a higher location), it becomes more dense and sinks below hotter fluid.

This causes the natural convection motion which allows for heat transfer from one location to another.

Since this only requires a substance which flows, it occurs in liquids as well as gasses.

In FIG. 2, air 5 near water 3 is heated. Air 5 becomes less dense and moves upward. In many prior art spas, there are gaps in the spa cover 110 and where the spa cover 110 meets the tub lip 133. Here air gap 11 is between the first part 111 and the tub lip 133. Another occurs where the second part 113 meets the tub lip 133.

The heated air 5 escapes upward through these gaps 11 and 13 and past skirt 170 as shown by arrows “A” and “B”, taking heat with it.

The hinge 150 is typically a thin flexible section between the first and second parts 111 and 113 of cover 110. A simple way to manufacture it is to have a thinner section connecting the first cover part 111 and the second cover part 113. Due to the geometry, when the cover 110 is placed on the tub 130, there are end openings 115 where the first part 111 meets the second part 113 at the hinge 150. Air also escapes out of these openings as marked by arrow “C”.

Attempts have been made to insert a long strip under hinge 150 to close the end openings 115. They run the length of the cover 110. The strip may fit tighter between the first part 111 and the second part 113 at a location other than near the tub lip 133. In this case, they do not completely close the end openings 115.

Therefore, the goal is to conserve energy by limiting the transfer of heat to the environment, thereby reducing energy costs.

FIG. 3 is a perspective view of one embodiment of the improved thermal cover according to the present invention.

A tub 1300 is covered by an insulated spa cover 1100 (Not Marked). It may be made of several parts. In this embodiment, there is the first part 1111 and the second part 1113. These are held together by a hinge 1150. These are made of insulating foam which is covered with a waterproof covering. Currently pending U.S. patent application Ser. No. 11/906,352 filed Oct. 2, 2007 by L. Livingston, E. Albert further describes various aspects of the cover. This pending patent application is hereby incorporated by reference as if set forth in its entirety herein.

First part 1111 and second part 1113 are allowed to be folded onto each other for removal or storage at hinge 1150. First part 1111 and second part 1113 typically have a top surface 1117, a bottom surface 1112 a, an inward surface 1112 b, and at least one other surface 1112 c connecting the top surface 1112 a to the bottom surface to the internal surface.

The present invention also includes a peripheral shield or 1170 attached at the top surface 1117 of cover 1100. This is continuously attached around the periphery of the cover 1100. It is typically 7″ to 9″ in length and has no gaps or openings. The shield 1170 is designed to extend downward, overlapping the interface between the tub lip 133 (Not Shown), the cover 1100, and the tub wall 135 (Not Shown).

Shield 1170 is designed to be continuous around the perimeter of tub 130 (Not Shown). Shield 1170 limits the escape of and captures the heated air from between the tub lip 133 (Not Shown) and the cover 1100, whereas current art designs only protect the spa lip. Alternately, a shroud 1171 includes or is integral combination of the top cover 1117 and shield 1170 formed to hold the first part 1111 and second part 1113.

A plurality of tie downs 2100, which may be belts, straps, or elastic material are attached near the top surface 1117 of spa cover 1100. In one embodiment, the tie down straps 2100 are on the order of 9″ long to extend over the shield which may be approximately 7″. The tie downs 2100 extend over spa cover 1100 and shield 1170 to attach at tie down attachments 2100 on the sides 135 of tub 130. In the prior art, there were tie downs which were under the skirt and functioned to hold the cover on the tub. In the present design, the tie downs 2100 are over the shield 1170.

FIG. 4 shows a cross sectional, side elevational view of the spa cover assembly 1000 according to the present invention as it would appear placed on a hot tub 130.

Although the shield 1170 reduces virtually all of the air escaping from tub 130, a small amount may become trapped in a buffer region or envelopment 1190. Heat transfer is dependent upon temperature difference between adjacent objects or materials. The temperature drop from the tub 130 to the hot air in buffer region 1190 is less than the temperature drop from the tub 130 to the environment 7 as in the prior art designs. This results in a lower amount of heat loss compared with the prior art designs.

Therefore, shield 1170 reduces the heat escape from the top of tub 130 as well as reducing the heat escape from the sides 135 of tub 130.

Since the first part and the second part of cover 1100 have to fold onto each other, a hinge 1150 can be on the inside of the cover 1100.

In the prior art design shown in FIG. 1, a strip of insulating material was placed in the space between the first part 111 and the second part 113 when deployed. This insulation strip would hang down from hinge 150 and was not attached to either the first part 111 or the second part 113. This would leak heat from both sides of the insulation strip.

Therefore, it is beneficial to provide the best seal between the first part 1111 and the second part 1113 at its edges. An abutment 1114 exists between the inward surface 1112 b of the first part 1111 and the inward surface 1112 b of the second part 1113.

FIG. 5 is a plan view of the spa cover 1100 of FIGS. 3 and 4 as viewed from below. As shown in FIG. 5, the first part 1111 meets the second part 1113 at a center line 1119. A central gasket 1151 is attached to the first part 1111 and fits under the hinge (1150 of FIGS. 3, 4) and seals against the second part 1113.

A central gasket 1151 is used to provide additional sealing where the first part 1111 meets the second part 1113. The central gasket 1151 is slightly wider than the longitudinal gap 1130 and compressible. When the first part 1111 and second part 1113 are closed, they press on central gasket 1151 to minimize heated air from escaping from the tub 130 through the hinge 1150.

FIG. 6 is a side view of the first part 111 and the second part 113 of a prior art spa cover 110 of FIG. 1. A skirt 170 may exist on some prior art spa covers 110, however, thee were on the order of 3″ and incapable of significantly holding in heat.

Some prior art spa covers 110 have a thermal strip 151 is attached at hinge 150 and hangs downwardly. When the parts 111 and 113 are fully opened, thermal strip 151 fits between them. However, if thermal strip 151 is hanging slightly lower or higher, or does not line up properly, gaps may form between the cover parts 111, 113 thereby producing a leaky seal.

FIG. 7 is a side view of the first part 1111 and the second part 1113 of the spa cover 1100 shown in FIGS. 3, 4. Here shield 1170 is connected to spa cover 1100 and is shown hanging down from the partially folded spa cover 1100. Since the shield 1170 is sufficiently long enough to conform when cover 1100 is folded.

Unlike the prior art embodiments, central gasket 1151 has one surface 1153 which is attached to first part 1111. This eliminates any potential gaps which may release heat under hinge 1150.

A second central gasket surface 1155 may optionally employ a releasable attachment means, such as a hook and loop attachment means similar to the attachment marketed as Velcro. This would cause central gasket surface 1155 to come in contact with, and attach to the second part 1113 eliminating gaps reducing the escape of heat.

The ends of hinge 1150 are critical since they meet tub lip at both sides at a tub lip/hinge interface 1158. As shown in FIG. 5, end gaskets 1157 may be employed, similar to the central gasket 1151. These are designed to be slightly wider than the central gasket 1151 and are compressible. Since they are slightly wider than the central gasket 1151, they will meet first part 1111 and second part 1113 before the central gasket 1151 thereby insuring a tight seal on the tub lip 133 on either side. Again, like the central gasket 1151, they may be attached to one of the cover 1100 parts to insure a seal. Again, they may also include an attachment means to close any gaps.

Therefore, an improved thermal spa cover is described which minimizes heat loss by convection by plugging up air leaks using a spa cover. It employs a shield, tie downs and buffer regions to reduce heat loss through convection as well as conduction.

It is of course understood that departures can be made from the preferred embodiments of the invention by those of ordinary skill in the art without departing from the spirit and scope of the invention that is limited only by the following claims. 

1. An improved thermal spa cover assembly for covering a tub having sidewalls filled with heated water having a lip comprising: a first part having a top surface, a bottom surface, an inward surface, and at least one other surface connecting the top surface to the bottom surface to the internal surface, the first part comprising a heat insulating material, a second part having a top surface, a bottom surface, an inward surface, and at least one other surface connecting the top surface to the bottom surface to the internal surface, the second part comprising a heat insulating material, a hinge pivotally connecting the first part to the second part, a shroud comprising a top cover and a shield, the top cover covering the first part and second part at the top surface (or integral with the top surface) and roughly occupying a plane approximately parallel with the first part and the second part, and the shield connected to or integral with the top surface, continuously extending from the top surface to a periphery, extending perpendicular to the plane, and adjacent to the sidewalls of the tub to make a gap free seal between the top cover and the periphery reducing the escape of heat.
 2. The assembly of claim 1, the hinge formed from the shroud.
 3. The assembly of claim 2, the hinge formed from the top cover of the shroud.
 4. The assembly of claim 1, further including a buffer region having a buffer region temperature and existing between the shield periphery, the top cover, and the sidewalls.
 5. The assembly of claim 4, further including an envelopment existing between the heated water and the first and second parts, the envelopment having an envelopment temperature.
 6. The assembly of claim 5, the tub disposed in ambient air having an ambient air temperature, and the envelopment temperature being greater than the buffer region temperature, and the buffer region temperature being greater than the ambient air temperature.
 7. The assembly of claim 1, further including an abutment existing between the inward surface of the first part and the inward surface of the second part at the location of the hinge, thereby forming a longitudinal channel having a channel length and a channel width.
 8. The assembly of claim 7, further including a central gasket comprising a first surface and a second surface, the first surface and second surface having a gasket length roughly equivalent to the channel length, the central gasket having a gasket width defined by the distance between the first surface and the second surface, said gasket width being larger than the channel width to assist in minimizing heat from escaping from the tub through the abutment, the first surface being attached to the inward surface of the first part.
 9. The assembly of claim 8, the second surface of the central gasket having a releasable attachment for engaging the second surface with the inward surface of the second part.
 10. The assembly of claim 8, the central gasket extending over the tub lip at one or more tub lip/hinge interfaces, and the gasket width widening to an end gasket width at the one or more tub lip/hinge interfaces to minimize heat leakage at said tub lip/hinge interfaces.
 11. The assembly of claim 7, further including one or more end gaskets located at one or more tub lip/hinge interfaces defined by a location where the tub lip and hinge are closest, each of the end gaskets comprising a first surface, a second surface, a tub lip surface for contacting the tub lip, and a hinge surface for contacting the hinge, each of the end gaskets having an end gasket width that is wider than the channel width, and the first surface of each of the end gaskets attached to the inward surface of the first part or the second part.
 12. The assembly of claim 11, the second surface of each end gasket having a releasable attachment for engaging the second surface with the inward surface of the second part or the first part.
 13. The assembly of claim 11, the central gasket made of a compressible material.
 14. A method of reducing heat loss from a tub filled with heated water comprising the steps of: providing an insulated first part having a top surface, the first part being constructed of a heat insulating material; providing an insulated second part having a top surface, the second part being constructed of a heat insulating material; pivotally connecting the first part to the second part; applying a continuous shield connected at the top surfaces of the first and second parts, the shield sized and positioned to hang down along side the tub; and placing the first and second parts and the shield over said tub to thermally insulate the hot water from the environment and to collect and retain escaping hot gases.
 15. The method of claim 14, further including the step of attaching a central gasket to the first part or the second part on a portion of the first part or second part that comes in contact with the other of the first part or the second part.
 16. The method of claim 15, further including the step of compressing the central gasket between a portion of the first part or second part that comes in contact with the other of the first part or the second part.
 17. The method of claim 14, further including the step of compressing a central gasket between a portion of the first part or second part that comes in contact with the other of the first part or the second part.
 18. A heat shroud for reducing heat loss from a spa having spa walls and a tub lip and covered with a piece of insulated material having a top surface defined by a top surface edge, the heat shroud comprising a first periphery and a second periphery connected together by a wall, the first periphery connected to the top surface edge, and the second periphery enveloping the tub lip and laying adjacent to the spa walls.
 19. The heat shroud of claim 18, the wall continuously extending uninterrupted from the first periphery to the second periphery. 